The present invention relates to a blood pressure measuring instrument, i.e., a sphygmomanometer and, more particularly, to an electronic sphygmomanometer with a voice synthesizer for speaking patient's systolic and diastolic pressures.
Conventionally, systolic blood pressure and a diastolic blood pressure are measured using an inflatable occluding cuff which usually is wrapped about a patient's limb so as to close, or completely occlude, an artery. Typically, the occluding cuff is wrapped about the arm in juxtaposition to the brachial artery. When the cuff is inflated to a pressure which exceeds the patient's systolic pressure, so as to close this artery, blood is no longer capable of flowing therethrough. As the cuff is slowly deflated, a point is reached where the patient's systolic pressure exceeds the cuff pressure. Consequently, the artery opens for a short period during the patient's cardiac cycle. Once the blood pressure during this cardiac cycle falls below the cuff pressure, the artery once again is closed.
The pressure in the cuff which is equal to the maximum blood pressure during a cardiac cycle is, of course, the systolic pressure. It is known that when the blood pressure exceeds the actual cuff pressure, resulting in the opening of the artery, turbulence in the blood stream is accompanied by a sound which is the so-called Korotkoff sound. These Korotkoff sounds occur each time the artery is opened. Thus, as long as the cuff pressure exceeds the lowest, or diastolic, pressure in the cardiac cycle, the artery will be alternately opened and closed as the cardiac cycle pressure traverses the cuff pressure. When the cuff pressure falls below the lowest pressure point in the cardiac cycle, the artery will remain opened, and the Korotkoff sounds no longer will be produced. Consequently, by measuring the cuff pressure at the last Korotkoff sound, a close approximation is made of the patient's diastolic pressure.
In the conventional electronic sphygmomanometer, an operator must read the systolic and diastolic pressures visually displayed in a digital or analog display. This may produce an erroneous reading. Therefore, an electronic sphygmomanometer has been developed wherein the systolic pressure and the diastolic pressure are audibly output through the use of a synthetic speech system. The combination of the audible output and the visual display provides accurate recognition.
However, of great importance and which should be considered is the fact that the blood pressure of a patient may be greatly influenced by the patient's awareness of the visual display or the audible output of his or her pressure.